The present invention relates to wind turbines including a rotor having a plurality of rotor blades attached to a hub, and especially relates to a method and an apparatus for adjusting a yaw angle of a wind turbine with respect to the wind direction at the location of the wind turbine.
Conventionally a wind turbine includes yaw brake control units and yaw motor control units in order to provide yaw brake driver signals and yaw motor driver signals which are used to adjust, in cooperation with a yaw angle adjustment unit, the yaw angle of the entire wind turbine. Furthermore wind turbines include yaw momentum sensors in order to measure a yaw momentum of the wind turbine. These kind of measurements usually are carried out in order to reduce the load on different components like main shaft and hub by adding interdependent or independent pitch offsets to each rotor blade. In order to reduce the load most effectively the yawing momentum is controlled to zero by adjusting the yaw angle of the wind turbine using the yaw angle adjustment unit.
Wind turbines are of increasing importance as an environmentally safe and relatively inexpensive energy source. Thus an increased demand for an improved wind turbine performance has let to efforts concerning an optimum adjustment of the yaw angle with respect to the wind direction at the location of the wind turbine. As the wind direction at the location of the wind turbine may rapidly change, the yaw adjustment unit has to provide a reliable adjustment of the yaw angle even for a varying wind direction. Wind turbines include actuator devices such as yaw motors and yaw brakes in order to rotate a machine nacelle with respect to the wind direction at the location of the wind turbine. This kind of actuator devices are usually large electrical drives with gear boxes. These systems are complicated and expensive because they have to provide a torque required to orientate the wind turbine towards the incoming wind direction.